He had to give up ______ the football match because he had his leg injured in the accident.

A．a machine using solar energy efficiently has already been developed
B．the sun is our final source of power
C．man uses only a tiny part of the sun's energy
D．the part of the sun's energy we use is used indirectly

A．harnessing energy through chemistry
B．our last source of power
C．how water power is produced
D．the amount of solar energy that can be utilized